Drag your car/Land vehicle mesh in the scene.
Select the main mesh for your vehicle and add a collider.
Ensure the collider does not overlap with the wheels.
The wheels will have their own colliders applied by the Car Physics script and those colliders should not overlap the body collider.
You can adjust the collider size manually by clicking the Edit Collider button and grabbing the small green dot in the middle of each surface, or by entering size and position parameters in the Inspector.
Car Vehicle Script
Attach the Car Vehicle component to your vehicle.
This will add three scripts to the object;
Check for active
Wheel FR / FL / BR / BL
Vehicle Rigid Body
Add the animation track from an FBX file here to apply a pose to the user's avatar while using the vehicle.